Purpose: Red blood cell distribution width (RDW) evaluates the variation (size heterogeneity) in red blood cells. Elevated RDW has been identified as a predictor of poor functional outcomes for acute ischemic stroke. The association between elevated RDW level and poor functional outcome in stroke patients undergoing mechanical thrombectomy has not been reported before. This study aims to investigate this relationship. Materials and Methods: This was a multicenter retrospective study involving the prospectively and consecutively collected data of 205 adult stroke patients who underwent mechanical thrombectomy for anterior circulation large vessel occlusion (middle cerebral artery M1, anterior cerebral artery A1, tandem ICA-MCA, carotid T) between July 2017 and December 2019. RDW cut off levels were accepted as >16%. The effect of elevated RDW on poor functional outcome (modified Rankin scale 3–6) was investigated using bivariate and multivariate regression analysis. Results: Elevated RDW was significantly associated with poor functional outcome in bivariate and multivariate analysis (odds ratio [OR] for RDW >16%, 2.078; 95% confidence interval [95% CI], 1.083–3.966; P=0.027 and OR for RDW >16%, 2.873; 95% CI, 1.342–6.151; P=0.007; respectively). Conclusion These findings suggest that elevated RDW may be an independent predictor of poor functional outcomes in ischemic stroke patients undergoing mechanical thrombectomy.